The conventional iron-less linear motor is disclosed in FIGS. 17 and 18 and comprises a stator X and a coil assembly Y which moves along the rail of the stator X. The stator X is composed of multiple permanent magnets M which are arranged in alternative pattern with gaps located there between so as to form the U-shaped rail having alternating N and S polarities. The coil assembly Y has multiple coil loops which are arranged to form the coil unit and the current with multiple phases is input, such as the well known three-phase coil unit. The coil unit has a resin package layer Z mounted thereto and installed in the recess of the board W.
Taiwan Patent Application No. 201126875 discloses a coil unit of a linear motor wherein the coil unit comprises multiple adjacent coil units, a base and a resin package layer. These coil loops form two linear function sides, a first non-function side and a second non-function side. The coil loops form multiple first bent sections which are alternative to each other on the first non-function side, and multiple conductive lines on the second non-function side. These conductive lines are connected to the exterior cables located outside of the coil unit. The base has a slot whose cross section is correspondent to the cross section of the first bent section. The coil loops are inserted in the slot. The resin package layer encloses the coil loops and seals the slot, thereby increasing the contact area between the coil loops and the insides of the slot and the efficiency for dissipating heat. The two linear function sides are alternative to each other to reduce the volume required for the coil unit.
U.S. Pat. No. 5,998,890 discloses a linear motor wherein the coil unit defines the shape of the coil loop which has two vertical function sides and two axial non-function sides. The relationship between the coil inside width (CIW) of the vertical function sides, the coil side width (CSW) and the number of phases of the current (#Φ) is expressed by the equation:CIW=CSW×(#Φ−1).Because of the shape, the coil loops can be overlapped tightly to reduce the space occupied by the coil unit.
However, along with the demands of higher output and speed for the linear motors, higher current and voltage are input into the linear motor and which generate higher heat and reduce the efficiency of the motor. The coil loops are arranged close to each other so that the heat is difficult to be dissipated and the risk of circuit short becomes high. The specific relationship of CIW=CSW×(#Φ−1) cannot provide extra room for the heat dissipating members or insulation members.
The present invention intends to provide a coil unit for linear motors and improves the shortcomings of the conventional ones.